Film transport system

ABSTRACT

Glassless film carrier for use in blowback systems for producing offset printing plates from microfilm. The film is moved between supply and take-up reels in discrete small steps by a stepping motor and drive capstan. Indexing marks are provided on the film at predetermined positions relative to the frames, and photosensors detect the indexing marks to determine when the frames are in position for projection. A slip clutch cooperates with the drive capstan to hold the film taut and flat, and rollers backbreak the film to eliminate its natural curl.

United States Patent [1 1 u 11 3,879,003 Gasser Apr. 22, 1975 FILM TRANSPORT SYSTEM Primary E,\'aminerLeonard D. Christian [76] Inventor: John Anton Gasser, l386-l9th Ave., g iff 2 3" or Hohbach' Test San Francisco, Calif. 94122 ether [22] Filed: May 16, 1973 57 ABS C TRA T [2]] Appl. No.: 360,633 1 Glassless film carrier for use in blowback systems for producing offset printing plates from microfilm. The [52] film is moved between supply and take-up reels in dis- 2; l h 242/l88 3 208 210 crete small steps by a stepping motor and drive cap- 1 le 0 184 lq fi l 'b 2 stan. indexing marks are provided on the film at predetermined positions relative to the frames, and pho- R t d tosensors detect the indexing marks to determine [56] e erences when the frames are in position for projection. A slip UNITED STATES PATENTS clutch cooperates with the drive capstan to hold the 2,917.250 12/1959 Bodcnstcin 242/188 X film taut and flat, and rollers backbreak the film to 3,026,056 3/1962 Nielsen 242/l88 eliminate its natural cur], 3.l84.l77 5/1965 Hannah 242/l88 13 Claims, 9 Drawing Figures PATENTEDAPRZZISYS sumunfs w wrk FILM TRANSPORT SYSTEM BACKGROUND OF THE INVENTION This invention pertains generally to film carriers and more particularly to a film carrier for use in a microfilm blowback system for use in producing offset printing plates.

Heretofore. micro systems have been used widely in information storage and retrieval. Recently, systems have been developed for producing plates from microfilm for use in offset printing. In such systems. the pages to be printed are photographed on microfilm. as in conventional systems for storing and retrieving information on microfilm. The images on the microfilm are then projected in an enlarger onto a negative working paper plate, such as the plate marketed by Eastman Kodak under the trademark Verilith. The plate is processed and utilized in an offset printing press in the conventional manner.

SUMMARY AND OBJECTS OF THE INVENTION The invention provides a film carrier for use in an automated system for producing offset printing plates from microfilm. According to the invention, the film is moved between supply and take-up reels by means of a capstan driven by a stepping motor. Indexing marks are provided on the film at predetermined positions relative to the picture frames. and photoelectric sensors detect the indexing marks to determine when the frames are aligned with the optical axis of the enlarger. A slip clutch cooperates with the drive capstan to tension the film and hold it taut in the focal plane. and rollers backbreak the film to eliminate its natural curl.

It is in general an object of the invention to provide a new and improved film carrier for use in an automated blowback system for making offset printing plates from microfilm.

Another object of the invention is to provide a film carrier of the above character which includes means for accurately positioning the film with respect to the optical axis and focal plane of an enlarger.

Another object of the invention is to provide a film carrier of the above character which utilizes a stepping motor to advance the film in discrete steps which are substantially shorter than the frames of the film.

Another object of the invention is to provide a film carrier of the above character which includes means for eliminating the natural curl of the film.

Additional objects and features of the invention will be apparent from the following description, in which the preferred embodiment is set forth in detail in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of one embodiment of an automated plate making system encorporating the film carrier of the invention.

FIG. 2 is a block diagram of a control system for the automated plate making system shown in FIG. 1.

FIG. 3 is a perspective view of a portion of a strip of microfilm for use in the film carrier of the invention.

FIG. 4 is a top plan view of one embodiment ofa film carrier incorporating the invention.

FIG. 5 is a cross-sectional view taken along line 5 -5 in FIG. 4.

FIG. 6 is a fragmentary cross-sectional view ofa sensing head used in the film carrier shown in FIG. 4.

FIG. 7 is a cross-sectional view taken along line 77 in FIG. 4.

FIG. 8 is across-sectional view taken along line 8-8 in FIG. 4.

FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT The automated plate making system illustrated in FIG. 1 includes an enlarger 11, a film carrier 12, a paper feed or transport assembly 13, and a control unit 14. The enlarger is preferably a special microfilm retrieval enlarger, such as a Durst Spec Micro II enlarger, and it has a head 16 and an easel 17 mounted on an upstanding column 18. Motors, not shown, are provided for moving the head and easel on the column and for making focusing adjustments. Film carrier 12, dis cussed hereinafter in detail, is mounted in the negative stage of the enlarger head in place of a conventional negative carrier. Paper drive assembly 13 rests on easel I7 and includes motive means for moving the plate paper from supply to take-up rolls. Control unit I4 is mounted in a separate cabinet 21 and connected to the enlarger, film carrier and paper drive by suitable cables. as indicated schematically by lines 22-24.

As is discussed more fully hereinafter. a film carrier 12 includes a drive motor 26 for advancing the film between supply and take-up reels and a sensing head 27 for detecting indexing marks on the film when the frames are aligned with the optical axis of the enlarger. As illustrated in FIG. 2, control unit 14 is connected to the drive motor and sensing head, the exposure control of enlarger l1 and paper drive 13. The control unit is also connected to the motors for adjusting the positions of the enlarger head and easel, as well as to the focus adjusting motor. whereby the head. easel and focusing can all be adjusted from the control unit.

In operation, drive motor 26 advances the film toward the take-up reel until one of the frames is aligned with the optical axis of the enlarger. At this time. control unit 14 deenergizes the drive motor to stop the film and initiates the exposure of the plate paper. When the exposure is completed, the control unit reenergizes the drive motor and energizes the paper drive to move the next plate into position for exposure. The process continues until plates have been made from the desired number of frames.

FIG. 3 illustrates a strip of microfilm 31 prepared with indexing marks 32 according to the invention. The strip is an enlongated strip of roll film having a plurality of frames 33 spaced longitudinally thereof. A pair of indexing marks 32 is provided for each frame. The marks are located at a predetermined position relative to the frame. and as illustrated, they are disposed along the edges of the film at the center line of each frame. In the preferred embodiment. the marks are rectangular cuts having a minimum width of 0.030 inch and a minimum depth of 0.060 inch. If desired, the marks can be provided along only one edge of the film. and they can have shapes other than rectangular. However. the marks preferably have at least one straight edge extending transversely of the film to provide a sharp line which can be accurately detected. The film can be prepared by conventional means such as a computer or a microfilm camera.

As illustrated in FIGS. 4 9, film carrier 12 comprises framework means including a central section 36 and reel supporting arms 37 and 38. Arms 37 and 38 extend from the ends of central section 36 and are secured thereto by threaded members 39. The central section of the framework is generally flat and of a size to fit in the negative stage of a conventional enlarger.

This section is formed to include a glassless window 36a which is aligned with the optical axis of the enlarger so that a frame in registration with the window can be projected.

Supply and take-up reels 41 and 42 are mounted near the outer ends of reel support arms 37 and 38, respectively. These reels are illustrated as being of different sizes to accommodate films of different widths, such as 16mm and 35 mm. to illustrate that the carrier can be used with films of different widths. It will be understood, however, that the supply and take-up reels would normally be of the same width. Supply reel 41 is mounted on a rotatably mounted shaft 43 and held on the shaft by a knurled retaining collar 44. Take-up reel 42 is rotatably mounted and driven by a take-up motor, as isdiscussed hereinafter in detail.

Means is provided for advancing film 31 from the supply reel to the take-up reel in discrete steps which are substantially shorter than frames 33. This means includes a drive capstan 46 and a stepping motor 47. The capstan is rotatably mounted in bearings 48 and 49 mounted respectively in support arm 38 and in a mounting bracket 51 which is affixed to the support arm by suitable means such as screws 52. The stepping motor is mounted on a bracket 53 which is affixed to the support arm by suitable means, such as screws, not shown. This motor is electrically energized, and in the preferred embodiment it rotates in steps on the order of 18 at a rate of 250 steps per second. The motor is connected to the capstan by means of a torque converter 54. In the preferred embodiment, the capstan has a diameter of 4 inch, and the film moves at a rate on the order of 1 inch per second in steps on the order of 0.004 inch.

A drive roller or pinch roller 56 is provided for urging the film into engagement with the drive capstan. This roller is rotatably mounted in an eccentric assembly 57 which provides means for adjusting the position of the roller relative to the capstan.- The eccentric assembly includes a drum 58 which is mounted in a circular bore 59 in support arm 38. Drum 58 is formed to include a bore 61 which is displaced from the axis of the drum. Roller 56 is mounted coaxially of bore 61 by means of bearings 62 and. therefore, eccentrically with respect to the axis and outer surface of drum 58. A lever 63 is affixed to drum 58 for adjusting the position of roller 56, and a set screw 64 is threadedly mounted in support arm 38 for engaging the drum to lock the roller in a desired position.

Means is provided for rotating take-up reel 42 to wrap the film thereon after it passes the capstan and drive roller. This means includes a torque motor 66 which is mounted on a mounting plate 67 affixed to support arm 38 by a spacer 68 and bolts 69. The takeup reel is mounted on a shaft 71 and constrained for rotation therewith by suitable means such as splining, not shown. The reel is held on the shaft by means of a retaining collar 72 and set screw 73. The set screw is threadedly mounted in the retaining collar and engages a groove 74 in shaft 71. The shaft is provided with a second groove 76 to accommodate a wider reel. Shaft 71 is rotatably mounted in bearings 77 carried by support arm 38, and it is connected to the output shaft of torque motor 66 by a torque converter 78. The torque motor can rotate the take-up reel only when the resistance to this rotation is below a predetermined level. This level is chosen to be less than the holding force exerted by the drive capstan and pinch roller so that the take-up reel will not draw the film past the capstan.

Stepped guide rollers are provided at spaced apart locations along the framework to provide means for guiding the film along a predetermined path between the supply and take-up reels. These rollers include a roller 81 mounted on support arm 37, rollers 82 and 83 mounted on central framework section 36, and a roller 84 mounted on support arm 38 between the drive capstan and take-up reel. These rollers are all similar in construction and the manner in which they are mounted. Each roller is stepped to accommodate films of different widths, and each is mounted on a fixed shaft by means of ball bearings. Thus, for example, roller 83 is mounted on a fixed shaft 86 by means of ball bearings 87, as illustrated in FIG. 7. An additional guide roller 88 is mounted on support arm 38 for guiding the film from the central section of the framework to the drive capstan.

Means is provided for yieldably resisting the movement of the film toward the drive capstan, whereby the film is tensioned and held taut as it passes over window 36a. This means includes a slip clutch 91 of the type commonly used for tensioning film in photographic equipment. This clutch is mounted on support arm 37 and connected to a roller 92 which engages the film. The film is urged into engagement with roller 92 by means of a pinch roller 93 and an eccentric assembly 96. This assembly is generally similar to eccentric assembly 57, and it includes an operating lever 97 and a lock screw 98.

Means is provided for backbreaking the film to eliminate the natural curl of the film from the supply reel. This means includes roller assemblies 101 and 102 disposed on opposite sides of window 36a in the central section of the framework. Roller assembly 101 includes spaced apart side plates 103 and 104 which are affixed to the framework by suitable means, such as screws, not shown. Rollers 106, 107 and 108 are mounted between the side plates, and guide roller 82 is mounted on afixed shaft carried by the plates. An additional roller 109 is mounted between roller 106 and the slip clutch assembly. Rollers 107 and 109 engage the lower side of the film, and rollers 82 and 106 engage the upper side ing the indexing marks on the film when the frames are aligned with window 36a and the optical axis of the enlarger. The sensing heads are similar to each other, and, as illustrated in FIG. 6, each includes a body 119. A horizontally extending slot 121 is formed in the body, and the edge of the film passes through the slot. ln the preferred embodiment, a light source 122 and a photosensitive device 123, such as a photocell, are used for detecting the indexing marks. The light source is preferably a point source or a sharply defined line source to provide means for accurately detecting the edges of the indexing marks. A control circuit is connected between photosensitive device 123 and stepping motor 47 for deenergizing the stepping motor when an indexing mark is detected by the sensing head. This control circuit is of conventional design, and it includes means for comparing signals from the photosensor with clock signals to distinguish the indexing marks from scratches on the film. ln the system shown in FIG. 1, the control circuit is included in control unit 14.

Carriage assemblies 126 and 127 are provided for ad justing the positions of the sensing heads in longitudinal and transverse directions. Carriage assembly 126 includes a base 131 which is affixed to the central section of the framework by screws, not shown. A transverse slide 132 is mounted on base 131 and adapted for movement transversely of the direction of film travel by means of bearings 133. A longitudinal slide 134 is mounted on transverse slide 132 and adapted for movement parallel to the direction of film travel in bearings 136. Sensing head 116 is attached to slide 134 by suitable means, such as screws, not shown.

Micrometer means, including coaxially disposed control knobs 141 and 142, is provided for adjusting the positions of slides 132 and 134 and sensing head 116. Knob 141 is provided with a threaded skirt 143 which engages a threaded member 144 which is affixed to side 132. Slide 132 can be moved toward or away from the film by rotating knob 141. I

Knob 142 is affixed to one end of a shaft 146 which is rotatably mounted in a bearing 147 carried by knob 141. A pinion 148 is affixed to the other end of shaft 146 and engages a rack gear 149 affixed to slide 134. Slide 134 can be moved in a direction parallel to the film travel by rotating knob 142. Shaft 146 is formed in telescoping sections so that the rack and pinion gears will remain engaged as the carriage assembly is moved in the transverse :direction.

Carriage assembly 127 is generally similar to carriage assembly 126. It includes a base 151, a transverse slide 152 and a longitudinal slide 153. Base 151 is affixed to the central section of the framework, slide 152 is slideably mounted on the base by means of bearings .154, and slide 153 is slideably mounted on slide 152 by means of bearings 156. Control knobs 157 and 158 are provided for adjusting the transverse and longitudinal positions of carriage assembly 127, and they function in a manner similar to knobs 141 and 142.

If the indexing marks are all disposed along one edge of the film, only one sensing head is required, and sensing heads 116 and 117 can be preset to accommodate films of different widths, such as 16 mm and 35 mm. Alternatively, if desired, one of the sensing heads and carriage assemblies can be omitted entirely, and the remaining head and assembly can be adjusted to accommodate the different films. Similarly, both heads can be used concurrently on a strip of film.

Operation and use of the film carrier can be described briefly. lt is assumed that the carrier has been loaded with film and placed in the negative stage of the enlarger. The film passes from supply reel 41 under roller 81, between rollers 92 and 93, over roller 109, under rollers 106 and 82, over roller 107, under roller 108, under roller 113, over roller 114, under rollers 83 and 116, over roller 88, between drive capstan 46 and pinch roller 56 and under roller 84 to take-up reel 42. One or both of the sensing heads is positioned by means of control knobs 141 142 and 157 158 for detecting the indexing marks on the film when the frames are in registration with window 36a and aligned with the optical axis of the enlarger. Eccentric assemblies 57 and 96 are adjusted to engage drive capstan 46 and roller 92 with the film. When stepping motor 47 is energized, the film advances in small steps toward the take-up reel until an indexing mark is detected by the sensors. Film passing the drive capstan is wound on the take-up reel by torque motor 66. When an indexing mark is detected, the control circuit deenergizes the stepping motor, stopping the film in position to be projected. The film is maintained taut in the vicinity of window 36a by the action of slip clutch 91 and roller 93 pulling against the drive capstan and pinch roller 56. Roller assemblies 101 and 102 backbreak the film to eliminate its natural curl and assure that it is flat in front of the window.

The invention has a number of important features and advantages. For example, the stepping motor and photosensors make it possible to stop the film accurately in the correct position for projection. The carriage assemblies with micrometer adjusting means permit accurate adjustment of the sensing heads and film position. There is no glass to detract from the quality of the image projected, and the film is effectively held flat in the focal plane of the enlarger. The carrier can accommodate film of two different sizes without adjustment.

It is apparent from the foregoing that a new and improved film transport system has been provided. While only the presently preferred embodiment has been de scribed herein, as will be apparent to those familiar with the art, certain changes and modifications can be made without departing from the scope of the invention as defined by the following claims.

1 claim:

1. ln a film transport system, framework means, supply and take-up reels mounted on the framework means, an elongated strip of film having a plurality of longitudinally spaced apart frames and indexing marks disposed at predetermined locations relative to said frames, drive means including an electrically energized stepping motor for moving the film in discrete steps from the supply reel toward the take-up reel, said steps being substantially shorter than the frames on the film, sensing means for detecting the indexing marks when the frames are in a predetermined position between the supply and take-up reels, and control means responsive to the sensing means for deenergizing the stepping motor to stop the movement of the film when one of the frames is in the predetermined position.

2. A film transport system as in claim 1 wherein the drive means further includes a drive capstan driven by the stepping motor and a pinch roller engaging the'film and urging it against the drive capstan.

3. A film transport system as in claim 2 further including torque motor means connected to the take-up means for rotating the same to wind the film thereon after said film moves past the drive capstan.

4. A film transport system as in claim 2 further including slip clutch means engaging the film between the supply reel and the drive capstan for yieldably resisting the movement of the film toward the take-up reel to tension the film and hold it taut.

' 5. A film transport system as in claim 4 furtherineluding roller means engaging the film between the slip clutch means and the drive capstan for holding the film in a predetermined plane at the predetermined posithe opposite side of the film intermediate each pair of rollers and deflecting the film in a direction opposite to the direction in which the film tends to curl from being wound on the supply reel.

7. A film transport system as in claim 1 further including micrometer means for adjusting the position of the sensing means longitudinally and transversely of the film.

8. In a film carrier for moving a strip of film between supply and take-up reels and stopping the film in a predetermined fixed position so that a frame on the film can be projected, framework means having a glassless window through which the frame can be projected, supply and take-up reels rotatably mounted on the framework means. means including a drive capstan and pinch roller for engaging the film and pulling it from the supply reel toward the take-up reel. means for rotating the take-up reel towind the film thereon, electrically energized stepping motor means connected to the drive capstan for rotating the same to move the film in discrete steps substantially shorter than the frame to be projected. means for detecting an indexing mark on the film and deenergizing the stepping motor means when the frame to be projected is aligned with the window in the framework means,and means for engaging the film and yieldablyresisting the pull of the drive capstan to tension the film and hold it taut as it passes the window.

9. ln a film transport system for moving a strip of film between supply and take-up reels and stopping the film in a predetermined position so that a frame on the film can be projected. the film having a plurality of longitudinally spaced frames and indexingmarks disposed at predetermined locations relative to the frames: framework means, supply and take-up reels mounted on the framework means, drive means including an electrically energized stepping motor for moving the film from the supply reel toward the take-up reel in discrete steps substantially shorter than the frames on the film, said drive means also including a drive capstan driven by the stepping motor and a pinch roller for engaging the film and urging it against the drive capstan, slip clutch means for engaging the film between the supply reel and the drive capstan for yieldably resisting the movement of the film toward the take-up reel to tension the film and hold it taut, sensing means for detecting the indexing marks when the frames are in a predetermined position between the supply and take-up reels, and control means responsive to the sensing means for deenergizing the stepping motor to stop the movement of the film when one of the frames is in the predetermined position.

10. A film transport system as in claim 9 further ineluding roller means for engaging the film between the slip clutch means and the drive capstan for holding the film in a predetermined plane at the predetermined position. I

11. A film transport system as in claim 10 wherein the roller means includes a pair of spaced apart rollers on each side'of the predetermined position for engaging the film on one side thereof and at least one roller disposedfor engaging the opposite side of the film intermediate eachupairof rollers and deflecting the film t in a direction opposite to the direction in which the film tends to curl from being wound on the supply reel.

12. In a film transport system for moving a strip of film between supply and take-up reels and stopping the film in a predetermined position so that a frame on the film can be projected, the film having a plurality of Iongitudinally spaced frames and indexing marks disposed at predetermined locations relative to the frames: framework means, supply and take-up reels mounted on the framework means, drive means including an electrically energized stepping motor for moving the film from the supply reel toward the take-up reel in discrete steps substantially shorter than the frames on the film, sensing means for detecting the indexing marks when the frames are in a predetermined position between the supply and take-up reels, control means responsive to the sensing means for deenergizing the stepping motor to stop the movement of the film when one of the frames is in the predetermined position, and micrometer means for adjusting the position of the sensing means longitudinally and transversely of the film.

l3. ln a film carrier for moving a strip of film between supply and take-up reels and stopping the film in a predetermined fixed position so that a frame on the film can be projected: framework means having a glassless window through which the frame can be projected, supply and take-up l reels rotatably mounted on the framework means, means including a drive capstan and pinch roller for engaging the film and pulling it from the supply reel toward the take-up reel, means for rotating the take-up reel to wind the film thereon, electrically energized stepping motor means connected to the drive capstan for rotating the same to move the film in discrete steps substantially shorter than the frame to be projected, means for detecting an indexing mark on the film and deenergizing the stepping motor meanswhen the frame to be projected is aligned with the window in the framework means, means for engaging the film and yieldably resisting the pull of the drive capstan to tension the film; and hold it taut as it passes the window, and means for straightening the film before it passes the window, said means for straightening comprising a pair of spaced apart rollers carriedby the framework means for engaging the inner side of the film from the supply reel, and at least one additional roller between the pair posite to the direction in which the film tends to curl.

supply reel.

from being wound on the a: =0: :l: i: 

1. In a film transport system, framework means, supply and take-up reels mounted on the framework means, an elongated strip of film having a plurality of longitudinally spaced apart frames and indexing marks disposed at predetermined locations relative to said frames, drive means including an electrically energized stepping motor for moving the film in discrete steps from the supply reel toward the take-up reel, said steps being substantially shorter than the frames on the film, sensing means for detecting the indexing marks when the frames are in a predetermined position between the supply and take-up reels, and control means responsive to the sensing means for deenergizing the stepping motor to stop the movement of the film when one of the frames is in the predetermined position.
 2. A film transport system as in claim 1 wherein the drive means further includes a drive capstan driven by the stepping motor and a pinch roller engaging the film and urging it against the drive capstan.
 3. A film transport system as in claim 2 further including torque motor means connected to the take-up means for rotating the same to wind the film thereon after said film moves past the drive capstan.
 4. A film transport system as in claim 2 further including slip clutch means engaging the film between the supply reel and the drive capstan for yieldably resisting the movement of the film toward the take-up reel to tension the film and hold it taut.
 5. A film transport system as in claim 4 further including roller means engaging the film between the slip clutch means and the drive capstan for holding the film in a predetermined plane at the predetermined position.
 6. A film transport system as in claim 5 wherein the roller means includes a pair of spaced apart rollers on each side of the predetermined position engaging the film on one side thereof and at least one roller engaging the opposite side of the film intermediate each pair of rollers and deflecting the film in a direction opposite to the direction in which the film tends to curl from being wound on the supply reel.
 7. A film transport system as in claim 1 further including micrometer means for adjusting the position of the sensing means longitudinally and transversely of the film.
 8. In a film carrier for moving a strip of film between supply and take-up reels and stopping the film in a predetermined fixed position so that a frame on the film can be projected, framework means having a glassless window through which the frame can be projected, supply and take-up reels rotatably mounted on the framework means, means including a drive capstan and pinch roller for engaging the film and pulling it from the supply reel toward the take-up reel, means for rotating the take-up reel to wind the film thereon, electrically energized stepping motor means connected to the drive capstan for rotating the same to move the film in discrete steps substantially shorter than the frame to be projected, means for detecting an indexing mark on the film and deenergizing the stepping motor means when the frame to be projected is aligned with the window in the framework means, and means for engaging the film and yieldably resisting the pull of the drive capstan to tension the film and hold it taut as it passes the window.
 9. In a film transport system for moving a strip of film between supply and take-up reels and stopping the film in a predetermined position so that a frame on the film can be projected, the film having a plurality of longitudinally spaced frames and indexing marks disposed at predetermined locations relative to the frames: framework means, supply and take-up reels mounted on the framework means, drive means including an electrically energized stepping motor for moving the film from the supply reel toward the take-up reel in discrete steps substantially shorter than the frames on the film, said drIve means also including a drive capstan driven by the stepping motor and a pinch roller for engaging the film and urging it against the drive capstan, slip clutch means for engaging the film between the supply reel and the drive capstan for yieldably resisting the movement of the film toward the take-up reel to tension the film and hold it taut, sensing means for detecting the indexing marks when the frames are in a predetermined position between the supply and take-up reels, and control means responsive to the sensing means for deenergizing the stepping motor to stop the movement of the film when one of the frames is in the predetermined position.
 9. In a film transport system for moving a strip of film between supply and take-up reels and stopping the film in a predetermined position so that a frame on the film can be projected, the film having a plurality of longitudinally spaced frames and indexing marks disposed at predetermined locations relative to the frames: framework means, supply and take-up reels mounted on the framework means, drive means including an electrically energized stepping motor for moving the film from the supply reel toward the take-up reel in discrete steps substantially shorter than the frames on the film, said drIve means also including a drive capstan driven by the stepping motor and a pinch roller for engaging the film and urging it against the drive capstan, slip clutch means for engaging the film between the supply reel and the drive capstan for yieldably resisting the movement of the film toward the take-up reel to tension the film and hold it taut, sensing means for detecting the indexing marks when the frames are in a predetermined position between the supply and take-up reels, and control means responsive to the sensing means for deenergizing the stepping motor to stop the movement of the film when one of the frames is in the predetermined position.
 10. A film transport system as in claim 9 further including roller means for engaging the film between the slip clutch means and the drive capstan for holding the film in a predetermined plane at the predetermined position.
 11. A film transport system as in claim 10 wherein the roller means includes a pair of spaced apart rollers on each side of the predetermined position for engaging the film on one side thereof and at least one roller disposed for engaging the opposite side of the film intermediate each pair of rollers and deflecting the film in a direction opposite to the direction in which the film tends to curl from being wound on the supply reel.
 12. In a film transport system for moving a strip of film between supply and take-up reels and stopping the film in a predetermined position so that a frame on the film can be projected, the film having a plurality of longitudinally spaced frames and indexing marks disposed at predetermined locations relative to the frames: framework means, supply and take-up reels mounted on the framework means, drive means including an electrically energized stepping motor for moving the film from the supply reel toward the take-up reel in discrete steps substantially shorter than the frames on the film, sensing means for detecting the indexing marks when the frames are in a predetermined position between the supply and take-up reels, control means responsive to the sensing means for deenergizing the stepping motor to stop the movement of the film when one of the frames is in the predetermined position, and micrometer means for adjusting the position of the sensing means longitudinally and transversely of the film. 